The long-term objective of this research program is to understand the underlying mechanisms of Developmental Coordination Disorder (DCD) and to provide a scientific basis for the evaluation, and interventions of children with this disorder. In elementary school, children with DCD are estimated to comprise up to 6 percent of the population (APA, 1994). These children are at risk for poor academic achievement, socio-emotional difficulties, and long-term health problems due to their lack of participation in physical activities. Previous work on children with DCD has focused primarily on perceptual or task deficits. This proposal examines the hypothesis that children with DCD have problems with the relationship between perception and action and more specifically with the ability to adapt this relationship to new environments and tasks (referred to as adaptive sensorimotor control). In this project, we combine behavioral and computational approaches to investigate this relationship in 7-year-old children with and without DCD in stable and changing sensorimotor environments. Four experimental paradigms are used (a visuomotor drawing task, two postural tasks, one with a driving visual stimulus and another with a driving somatosensory stimulus, and an auditory bilateral tapping task). Thus, we examine the children across multiple motor tasks (drawing, posture, tapping), varying modalities (visual, touch, auditory), and varying time-scales (real-time, short-term adaptation or learning and developmental-time). Such experimental variations are included to address the issue of heterogeneity in this population and more specifically the claim that there are subtypes of DCD that may be task and/or modality dependent for identification. The specific aims of this proposal are to behaviorally and computationally: 1) Characterize the sensorimotor relationships across four tasks. We hypothesize that children with DCO will have less well-defined sensorimotor deficits in all tasks as indexed by measures of spatial and temporal accuracy and variability. Individually, children with DCD will show differential sensorimotor deficits across tasks indicative of the heterogeneity (and possible subtypes) of this population. 2) Investigate the learning of novel internal models under gradual and step-like changes in sensorimotor relationships across four tasks. We hypothesize that children with DCD will be less able to adapt to changes as indexed by time-course, spatial and temporal accuracy and variability measures. Individually, children with DCD will demonstrate differential effects with the abrupt and gradual changes reflecting different underlying mechanisms. 3) Investigate sensorimotor switching across four tasks. We hypothesize that children with DCD will demonstrate an averaging between sensorimotor relationships and/or take longer to stabilize their sensorimotor performance after experiencing a second novel sensorimotor relationship. And 4) Characterize the developmental changes in sensorimotor relationships and adaptations across four tasks after two years. We hypothesize that children with DCD will continue to show broad and non-adaptive sensorimotor tuning as indexed by measures in experiments related to specific aims #1 -3. Taken together, the information from these specific aims will lay the groundwork for future intervention studies as well as further investigation into the underlying mechanisms of this movement disorder.